The invention relates to beverage heating systems, and more particularly to a water heating system designed for an aircraft beverage maker that utilizes heated water in the preparation of coffees, teas, espressos, and the like.
Commercial aircraft have traditionally provided hot beverages, such as coffee and tea, to their passengers. To that end, galleys of commercial airlines typically include a beverage maker that can be used to prepare coffee, espresso, cappuccino, teas, and the like. As with many components within a commercial aircraft, such beverage makers must be compact and light-weight, and yet provide robust operations. In traditional designs for beverage makers, water is stored in a heating tank prior to use. The tank heats the entire volume of water to a desired temperature. Once heated, the water is directed to a brew basket for infusing with the coffee or other product. U.S. Pat. No. 7,861,644 describes an apparatus for brewing beverages, including a three heater system for an aircraft brewing system. In the '644 patent, as is typical in such systems, each heater is a single phase heating element. In this type of system, when one of the heaters is turned off to regulate the water temperature or fails, an imbalanced electrical load can result, which in turn violates most commercial aircraft electrical requirements.
Because most commercial aircraft incorporate three-phase power systems, the electrical appliances on such aircraft must be designed to utilize the three-phase power service. Three-phase power is used because it is more economical and dependable than equivalent single phase systems at the same voltage. In a three-phase system, three circuit conductors carry three alternating currents of the same frequency but different phases, so that each current reaches its respective peak value at a different time from the other two currents. The intent of the three-phase design is that the phase currents cancel out one another, summing to zero when the electrical load is linearly balanced. This results in a constant power transfer, which reduces generator and motor vibrations.
Typically, each phase voltage differs by only a few volts. If voltages differ greatly, a load imbalance can result that can result in system problems such as overheating, damage, undue motor stress and wear, and damage to connected components. The most excessive case of load imbalance is when a phase is completely lost or shut down. The present invention is designed to avoid phase voltage imbalances and provide a safer, more reliable beverage heating system.